#!/usr/bin/env python2
# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai

__license__   = 'GPL v3'
__copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
__docformat__ = 'restructuredtext en'

import struct

class Unavailable(Exception):
    pass

class NoRaster(Exception):
    pass


class DIBHeader(object):

    '''
    See http://en.wikipedia.org/wiki/BMP_file_format
    '''

    def __init__(self, raw):
        hsize = struct.unpack(b'<I', raw[:4])[0]
        if hsize == 40:
            parts = struct.unpack(b'<IiiHHIIIIII', raw[:hsize])
            for i, attr in enumerate((
                'header_size', 'width', 'height', 'color_planes',
                'bits_per_pixel', 'compression', 'image_size',
                'hres', 'vres', 'ncols', 'nimpcols'
                )):
                setattr(self, attr, parts[i])
        elif hsize == 12:
            parts = struct.unpack(b'<IHHHH', raw[:hsize])
            for i, attr in enumerate((
                'header_size', 'width', 'height', 'color_planes',
                'bits_per_pixel')):
                setattr(self, attr, parts[i])
        else:
            raise ValueError('Unsupported DIB header type of size: %d'%hsize)

        self.bitmasks_size = 12 if getattr(self, 'compression', 0) == 3 else 0
        self.color_table_size = 0
        if self.bits_per_pixel != 24:
            # See http://support.microsoft.com/kb/q81498/
            # for all the gory Micro and soft details
            self.color_table_size = getattr(self, 'ncols', 0) * 4


def create_bmp_from_dib(raw):
    size = len(raw) + 14
    dh = DIBHeader(raw)
    pixel_array_offset = dh.header_size + dh.bitmasks_size + \
                            dh.color_table_size
    parts = [b'BM', struct.pack(b'<I', size), b'\0'*4, struct.pack(b'<I',
        pixel_array_offset)]
    return b''.join(parts) + raw

def to_png(bmp):
    # ImageMagick does not convert some bmp files correctly, while Qt does,
    # so try Qt first. See for instance:
    # https://bugs.launchpad.net/calibre/+bug/934167
    # ImageMagick bug report:
    # http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=20350
    from PyQt4.Qt import QImage, QByteArray, QBuffer
    i = QImage()
    if i.loadFromData(bmp):
        ba = QByteArray()
        buf = QBuffer(ba)
        buf.open(QBuffer.WriteOnly)
        i.save(buf, 'png')
        return bytes(ba.data())

    from calibre.utils.magick import Image
    img = Image()
    img.load(bmp)
    return img.export('png')


